Conventionally, in the food production field or the like, an electrolysis water-making apparatus electrolyzes various electrolyte solutions (a raw material solution including a chlorine ion) so as to make electrolysis-sterilized water (electrolysis water), and the electrolysis-sterilized water is used for sterilization, disinfection or the like. For example, when an electrolyte solution including a chlorine ion such as a sodium chloride solution or a hydrochloric acid solution is electrolyzed, chlorine gas is produced through electrolytic oxidation, and by dissolving the chlorine gas in water, hypochlorous acid is generated. The electrolysis-sterilized water including the generated hypochlorous acid has many advantages compared to sterilized water prepared by dissolving sodium hypochlorite in water, such as the electrolysis-sterilized water exerts an excellent sterilization effect even when the chlorine concentration thereof is low, or it is not necessary to perform delicate concentration adjustment at each time of use.
The electrolysis water-making apparatus includes an electrolytic cell used to electrolyze an electrolyte solution, and a water supply system used to supply the electrolyte solution to the electrolytic cell. In addition, as the electrolytic cell, a bipolar electrolytic cell (series electrolytic cell) in which a plurality of electrode plates are arranged in series is widely used. The bipolar electrolytic cell is configured so that a plurality of electrode plates are arranged at intervals in a casing, an anode electrode and a cathode electrode are connected using welding to the electrode plate at one end in the axial direction thereof and to the electrode plate at the other end respectively, and electricity is conducted from the electrode plate (anode) at the one end via intermediate electrode plates to the electrode plate (cathode) at the other end.
In the electrolysis water-making apparatus, the water supply system supplies an electrolyte solution into the casing of the electrolytic cell, an electric current flows by applying a predetermined voltage to the electrolyte solution including chloride while the electrolyte solution is circulated, and chlorine gas is generated through oxidation reaction at the anode. The chlorine gas (or a liquid in which the chlorine gas is mixed) is removed from the electrolytic cell and is mixed with water, whereby hypochlorous acid is generated in the water, and electrolysis-sterilized water is made.
On the other hand, when the voltage applied between the electrodes of the electrolytic cell is cut off, thereby stopping electrolysis, and when a pump to supply an electrolyte solution to the electrolytic cell is stopped, an electrolyzed solution in which high-concentration chlorine gas or hypochlorous acid, non-electrolyzed hydrochloric acid, or the like is mixed remains in the electrolytic cell. In addition, in the present invention, such a remaining liquid in the electrolytic cell is referred to as the electrolyzed solution. When operations of the electrolytic cell and the pump are stopped, the electrolyzed solution in the electrolytic cell may flow back into a pipe (tube) connecting the electrolytic cell and the pump. By the flowback of the electrolyzed solution, corrosion of component parts such as a pump may occur due to chlorine gas or the like, and the lives of the component parts may be shortened.
Contrary to this, in the related art, a means of providing a check valve in a pipe connecting the electrolytic cell and the pump or a means of controlling the pump so that the operation of the pump used to supply an electrolyte solution is stopped after a lapse of a predetermined time in a state where the voltage applied between the electrodes of the electrolytic cell is stopped is adopted. Accordingly, the flowback of the electrolyzed solution from the electrolytic cell is prevented (for example, refer to Patent Document 1).